1. Field of the Invention
Embodiments of the present invention relate to fuel vapor processing apparatus used mainly for vehicles, such as automobiles, for adsorbing by an adsorption material fuel vapor produced in a fuel tank and purging fuel vapor desorbed from the adsorption material into an internal combustion engine.
2. Description of the Related Art
Fuel vapor processing apparatus generally include an adsorption material (e.g., activated carbon) filled into a case for adsorbing fuel vapor and allowing desorption of fuel vapor. Fuel vapor may be introduced into the case so as to be adsorbed by the adsorption material. Fuel vapor adsorbed by the adsorption material may be desorbed by a flow of air flowing through the case and then may be purged into the engine, more specifically, an intake air passage of the engine. JP-A-63-150459 teaches a fuel vapor processing apparatus having a heater for heating an adsorption material, so that the adsorption material may be heated by the heater during desorption in order to improve the desorption efficiency of fuel vapor.
In the case of the fuel vapor processing apparatus disclosed in JP-A-63-150459, the heater is operated (or electrically energized) after a residual amount of fuel vapor adsorbed by the adsorption material has been reduced to a predetermined value. Therefore, during the time when the heater is not operated (or not electrically energized), the temperature of the adsorption material may be lowered due to vaporization latent heat of fuel vapor, resulting in lowering the desorption efficiency. For this reason, there has been a problem that the time required for the desorption process becomes longer. If the time for operation of the heater is lengthened in order to this problem, it may cause increase in power consumption (energy consumption).
Therefore, there has been a need in the art for minimizing the time necessary for a desorption process of a fuel vapor processing apparatus and for reducing the power consumption of the heater.